北邮高级计算机网络课件

LANTechnologies

InformationNetworkCenter

BeijingUniversityofPostsandTelecommunications

〜2013

i

Objectives

oIdentifythepositionofdatalinklayerinthe

OSI/rmstructure.

oIdentifyanddescribethebasicoperationof

EthernetandotherLANtechnologies.

oDescribehowEthernetandIEEE802.3nodes

respondtocongestionproblems.

oIdentifythetypesofphysicalconnectorsand

cablingcommonlyusedwithdifferentLANs.

oIdentifytherelationshipofadjacentlayersto

DLL.

oDistinguishbetweenthevariousversionsof

IEEE802.3implementations.

oProspectthefutureofhighspeedLAN

technologies.

2

Majortopics

oLANProtocolArchitecture

oStandards

oMajorTechnology

Ethernet/FastEthernet/GbE/lOGbE

TokenRing

•FDDI

WirelessLAN

oCharacteristicsofLANs

3

LocalAreaNetworks

oOptimizedforamoderatesizegeographic

area.

oAlldevicesareattachedtoashared

medium.

oAtransmissionfromanyonedevicecan

bereceivedbyallotherdevicesattached

tothesamenetwork.

oMediumaccesscontrol(MAC)protocols

arerequiredtoarbitratestheaccessto

thesharedmediumsinceonlyonestation

shouldbeallowedtousethemediumata

time.

4

LANProtocolArchitecture(IEEE802

referencemodel)

OSIKekreiHT

oArchitectureModel

developedbyIEEE

802committee

oLowerlayersof

OSImodel

Physical

Logicallinkcontrol

(LLC)

Mediaaccess

control(MAC)

5

LAN协议结构

LANProtocolArchitecture

oLogicallinkcontrolOSIRritrtiHe

Model

layer

Interfacetohigher

levels

Providesaddressing

anddatalinkcontrol

functionalities

oMediumAccess

Controllayer

Governaccessto

transmissionmedium

ForthesameLLC,

severalMACoptions

maybeavailable

6

MAC协议

MACProtocols

oChannelPartitioning(Reservation)

Dividechannelintosmaller"pieces"(timeslots,

frequency)

Allocatepiecetonodeforexclusiveuse

oRandomAccess(Contention)

Allstationscontendfortimeonthemediumtransmitting

wheneverthetransmissionmediumismadeavailable-

Allowcollisions

"recover"fromcollisions

o“Takingturns"(RoundRobin)

Eachstationinturnisgiventheopportunitytotransmit

Duringtheopportunity,thestationmaydeclineto

transmitormaytransmitsubjecttoaspecifiedupper

bound

Whenastationfinished,itrelinquishesitsturn,andthe

rightispassedtothenextstation

7

MACProtocols(comparison)

oManystationshavedatatotransmit

Roundrobintechniqueswillbeefficient

oOnlyafewstationshavedatatotransmit

Overheadinpassingturnfromstationto

stationasmoststationwillnottransmit

Streamtrafficsuchasvoicecommunication

(lengthyandfairlycontinuous)

oReservationtechniques

Burstytrafficsuchasinteractiveterminaltype

traffic(shortandsporadic)

oContentiontechniques

8

OSIReference

ModelOSIProtocolSuite

_jCMIPDS|_^门~八”「j7HsVTF「

ASES

ApplicationACSE11ROSE11RTSE||CCRSE||二・.|

PisssntationPresentationS©ivICG.-'PresentationProtocol

SesssionSessionSSIVIC©.'SessionProtocol

TranspoilTPOTP1TP2TP3TP4

CONP/CMNSCLNP/CLNS

Network

IS-ISES-IS

DataLinkIEEE802.3耗三管⑸|乂”

802.2TokenRingFDD

PhysicalIEEE802.3TokenRingFDDIX.25

HairKvar©Handwar©HanchvareHanchvar©

9

Majortopics

oLANProtocolArchitecture

oStandards

oMajorTechnology

Ethernet/FastEthernet/GbE/lOGbE

TokenRing

•FDDI

WirelessLAN

oCharacteristicsofLANs

10

MilestonesforEthernet

o1982/10IEEE802.3

o1990/4Switch

o1993Fullduplex

o1995/3100MbpsIEEE802.3p

o1998/61000MbpsIEEE802.3z,ab

o2000/1010GIEEE802.3ae

o2010/640G/100G802.3ba

http:〃www上/new/source/226.html

ii

LANStandards

oANSI/IEEEStd8021990,IEEEStandardsforLAN/MAN:

OverviewandArchitecture.

o802.IB1992,IEEEStandardsforLocalandMetropolitanArea

Networks:LAN/MANManagement.

o802.21989LLC

o802.31993(CSMA/CD)Type10BASE-X

o802.3u1995100MbpsFastEthernet

o802.3z1998GigabitEthernet,onfiberopticcable

o802.4Token-PassingBusSpecifications

o802.5eTokenRingSpecifications

o802.6DistributedQueueDualBus(DQDB)forMAN

o802.71989,BroadbandLocalAreaNetworks

o802.8FiberOpticTAG

o802.9IsochronousServicesCSMA/CDMACService

o802.101992,IEEEStandardsforInteroperableLAN/MAN

Security

o802.12,LAN/MANDemandPriority

LANStandards(Conf)

o802,11WirelessLANWorkingGroup

o802.14CableModemWorkingGroup

o802.15WirelessPersonalAreaNetwork(WPAN)

WorkingGroup

o802,16BroadbandWirelessAccessWorkingGroup

o802.17ResilientPacketRingWorkingGroup

o802.18RadioRegulatoryTAG

o802.19CoexistenceTAG

o802.20MobileBroadbandWirelessAccess(MBWA)

WorkingGroup

o802.22WirelessRegionalAreaNetwork(WRAN)

13

IEEE802family

f

z

n

o

w•8022LOGICALLINKCOMTROL

sLlJ

crn

Ol

LoH

z

COMUJlDATA

B-u

工s802.1BRIDGING

uLINK

QcLAYER

<

II<z

4<

Ms

山802.3802.4802.5802.6802.9802.11802.1280214

一L

A・MEDIUMMEDIUMMEDIUMMEDIUMMEDIUMMEDIUMMEDIUMMEDIUM

H0e

W8ACCESSACCESSACCESSACCESSACCESSACCESSACCESSACCESS

>

O

N

o802.3802.4802.5802.6802.9802.11802.12802.14PHYSICAL

©PHYSICSPHYSICALPHYSICALPHYSICALPHYSICALT-JPHYSICALLAYER

,FomieflvIEEEStd802.1A.

14

StandardizedMediumAccessControl

Techniques

BusTopologyRingTopology

RoundRobinTokenBusTokenRing

(IEEE802.4)(IEEE802.5,

FDDI)

ReservationDQDB(IEEE

802.6)

ContentionCSMA/CD

(IEEE802.3)

15

主要的LAN技术

CommonLANtechnologies

100BaseTTokenRing/IEEE802.5

16

主要技术要点

MajorTechPoints

oTopology

oMediaaccess

oAddressscheme

oProtocolstack

oTransmissionmedia

oTransmissionmethod

oDevice

oSpecifictechnologies

17

Majortopics

oLANProtocolArchitecture

oStandards

oMajorTechnology

Ethernet/FastEthernet/GbE/lOGbE

TokenRing

•FDDI

WirelessLAN

oCharacteristicsofLANs

18

EthernetTechnology

19

AdrawingofthefirstEthernet

systembyBobMetcalfe

“AltoAlohaNetwork^^

to

"luminiferousether99network

20

Ethernetinearlydays

oEthernetisabasebandLANspecificationinvented

byXeroxCorparound70Jsthatoperatesat10

Mbpsusingcarriersensemultipleaccesscollision

detect(CSMA/CD)torunovercoaxialcable.

oThetermEthernetisoftenusedtorefertoall

CSMA/CDLANs.Ethernetwasdesignedtoservein

networkswithsporadic,occasionallyheavytraffic

requirements.

oEthernetVersion2.0wasjointlydevelopedby

DigitalEquipmentCorp.,IntelCorp.,andXerox

Corp.WhichcommonlyknownasDIX.Itis

compatiblewithIEEE802.3.

oTheIEEE802.3specificationwasdevelopedin

1980basedontheoriginalEthernettechnology.

21

EthernetHistory

o1970sALOHAo1980EthernetDIX

o1973Robertvl.O

Metclafe'sresearchato1982EthernetDIX

Xeroxv2.0

2.94Mbps,CSMA/

CDo1983IEEE802.3

o1976StarcomputerStandardApproved

defineda10Mbpso1995IEEE802.3|J

version

100Mbps

o1979DIXconsortium

o1980-83Standardso1998IEEE802.3z

Path1000Mbps

FromDIXto802.3o2002IEEE802.3ae

lOGbps

o2010IEEE802.ba:

40/100Gbps

22

Ethernetontheweb

o10Mbps

/ethernet/

10mbps.html

o100Mbps

olGbps

/

olOGbps

•http://www.lOgigabit-ethernet.com

olOOGbps

/

23

相关介质

EthernetFamily

oEthernetoperateat10Mbpsover

coaxialcable

o100Mbps,knownasFastEthernet,

operatesat100Mbpsovertwisted-pair

cable,alsoonDpticalfiber

o1000Mbps,knownasGigabitEthernet,

thatoperatesat1000Mbps(1Gbps)

overopticalfiberandtwisted-paircable

o10GEthernetoperatesatlOGbpsover

opticalfiber

o100GEthernetoperatesatlOOGbps

overopticalfiber

24

EthernetMigration

olOMb/stolOOMb/s

Shrinkthecollisiondomain

Onlytworepeaters

olOOMb/stolGb/s

Extendcarriertoallowmeaningfulcollision

domain

Onlyonerepeater

olGb/stolOGb/s

MakelOGbEfullduplexonly,nocollision

domain

25

Namingconvention10Base^1

BASE-y数据率（M匕时）基带或宽带段最大长度（百米）

CharacteristicEthernetValueIEEE802.3Values

Datarate1010Base510Base2lOBaseTlOBaseFlOOBaseT

(Mbps)

10101010100

SignalingBasebandBasebandBasebandBasebandBasebandBaseband

method

Maximum5005001851002000100

segment

length(m)

Impedance50Q50Q50Q100Q100Q

MediaThickcoaxThickThinCoaxUTPFiber-opticUTP

coax

TopologyBusBusBusStarP-to-PBus

xBASE-y<datarateinMbpsxsignalingmethod><maximumsegmentlengthinhundredsofmeters义6

协议结构

ProtocolArchitecture

oDefineslayers1and2specifications

Physicallayer(layer1)

oProvidestheelectrical,mechanicaland

Droceduralspecsforthetransmissionof

Ditsthroughacommunicationlink,

mediumorchannel

Datalinklayer(layer2)

oEnsureserrorcontrolandsynchronization

betweentwoentities

oIncludesMediumAccessControl(MAC)

andLogicalLinkControl(LLC)sub-layers

27

MAC接入控制

MediaAccessControl

oAddress

oCSMA/CD

oCollisioncontrol

oOperationmode

Half-duplex

Full-duplex

oDeviceimplementation

28

以太网地址

EthernetAddress

oGlobalunique

oAssignmentmanagement

byXerox,laterbyIEEE

o48bitlong

oVendorSection+Node

address

00:80:C8:8A:35:5F

oSingle-cast/Multicast/Broadcast

29

MAC子层的地址问题

oIEEE802标准为每个DTE规定了一个48位的全局地址，相

当于站点的唯一标识符，与其物理位置无关

oMAC地址字段可以采用两种形式之一：

6B全球范围，2B单位范围

o地址块：地址字段的前3个字节（高24位）由IEEE统一分

配给厂商，低24位由厂商分配；

o地址类型标识：地址字段的第一字节的最低位I/G0••单

个站地址；1••组地址

o地址范围标识：地址字段的第一字节的最低第二位U/L0-

局部管理；1“全局管理

1146115

I/GU/L46位地址I/G15位地址

30

什么是广播地址

Whatisabroadcastaddress?

oTheuniqueaddressthatidentifiesa

packetasappropriatetoall

receivingstations.

oExample

ff：ff：ff：ff：ff：ff

31

如何检查MAC地址

HowtocheckMACaddress

oWin95/98/2000,WinNT,DOS,XP

c:\arp-a

c:\winipcfg-c:\ipconfig/all

oUNIX/Linux

ifconfig-a

oNovell

intheServerconsole

oSniffer

oRouter

showarp...

o

32

MAC类型

MACtypes

oThereare2MACprotocolsdefinedfor

.Ethernet

,Half-duplex

•Full-duplex

oHalf-duplexisthetraditionalformof

Ethernet

Datatransmissioninonedirectionatatime

UsesCSMA/CDprotocol

oFull-duplexbypassestheCSMA/CD

protocol

Full-duplexmodeallowstwostationsto

、、simultaneouslyexchangedataoverapointto

全双工定义pointlinkthatprovidesindependenttransmit

andreceivepaths

33

CSMA/CD半双工

CSMA/CD(Half-Duplex)

oAnystationonaCSMA/CDLANcanaccessthe

networkatanytime.

oBeforesendingdata,CSMA/CDstationslistenfor

trafficonthenetwork.

oAstationwantingtosenddatawaitsuntilitdetectsno

trafficbeforeittransmits.

oAfterapacketistransmitted,thestationlistenstothe

channelwhilethetransmittedpacketisintransitover

thecable.

oIfnocollisionisdetected,thepacketissuccessfully

transmitted.

oIfacollisionisdetectedduringtransmission,then

transmitabriefjammingsignaltoinformother

stationsofthecollision,andimmediatelycease

transmission.

34

CSMA/流

CSMA/CDFlow

Stationisready

tosend

Waitaccordingto

NewAttempt

BackoffStrategy

八

Transmitdata&CollisionDetectedTransmitJam

sensechannelSignal

INoCollisionDetected

TransmitComplete

J5

二进制指数退避算法

TruncatedBinaryExponentialBackoff

Algorithm

oBinaryexponentialbackoffalgorithmwhen

collisionsoccur:

Iftwostationscollide,theneachstationwaits

either0or1slotbeforeattempting

retransmission

Ifasecondcollisionoccurs,thenthewaitingtime

israndomlychosenfrom0..3slots

Ifaftericollisions,waitingtimeisselected

randomlyfrom0to2L1slots

After10collisionstherandomintervalisfixedat

1023slots

After16collisions,thecontrollerreportsfailureto

thesender

36

Collision1

37

Collision2

□□

Stat沁nA

I1010101010

1010101010n

StationB

38

Collision3

StationB

39

Collision4

40

Collision5

41

Speedcalculation

ospeedoflightinavacuum

300,000,000meters/second

ospeedofelectricityinacopper

cable

200,000,000meters/second

olOMbpsEthernet:

(200,000,000m/s)/(10,000,000

bits/s)=20metersperbit

42

全双工MAC类型

Full-duplexMACTypes

oBasedontheIEEE802.3xstandard,FD

MACtypebypassestheCSMA/CDprotocol

oFDmodeallowstwostationsto

simultaneouslyexchangedataovera

pointtopointlink

oAggregatethroughputofthelinkis

effectivelydoubled

FD100Mb/sstationprovides200Mb/sof

bandwidth

oFDoperationisrestrictedtopointtopoint

linksconnectingexactlytwostations

oUsedin1/10GbEonly.

43

EthernetandIEEE802.3Frame

Formats

FieldLength,

inBytesEthernet

866246-15004

PreambleDestinationSourceTypeDataFCS

AddressAddress

FieldLength,

inBytesIEEE802.3

7166246-15004

S

PreambleODestinationSourceLength802.2HeaderFCS

FAddressAddressandData

SOF=Start-of-FrameDelimiter

FCS=FrameCheckSequence

44

EthernetandIEEE802.3FrameFields

oPreamble--Alternatingpatternofonesand

zerosthattellsreceivingstationsthataframe

iscoining(EthernetorIEEE802.3),The

Ethernetframeincludesanadditionalbyte

thatistheequivalentoftheStartofFrame

(SOF)fieldspecifiedintheIEEE802.3frame.

oStart-of-Frame(SOF)--TheIEEE802.3

delimiterbyteendswithtwoconsecutive1

bits,whichservetosynchronizetheframe

receptionportionsofallstationsontheLAN.

SOFisexplicitlyspecifiedinEthernet.

45

EthernetandIEEE802.3FrameFields

(Cont')

oDestinationandSourceAddresses--

Thefirst3bytesoftheaddressesare

specifiedbytheIEEEonavendor­

dependentbasis.Thelast3bytesare

specifiedbytheEthernetorIEEE

802.3vendor.

oThesourceaddressisalwaysaunicast

(singlenode)address.

oThedestinationaddresscanbe

unicast,multicast(group),or

broadcast(allnodes).

46

EthernetandIEEE802.3FrameFields

(Conf)

oLength/Type

Type(Ethernet)--Specifiestheupper-layer

protocoltoreceivethedataafterEthernet

processingiscompleted.

Length(IEEE802.3)—Indicatesthenumberof

bytesofdatathatfollowthisfield.

oData(Ethernet)—Datacontainedinthe

frame.Afterphysicallayerandlinklayer

processingiscompleted,thisdataissentto

anupper-layerprotocol.Theupper-layer

protocolisidentifiedintheTypefield.

47

EthernetandIEEE802.3FrameFields

(Conf)___________________

oAlthoughEthernetVersion2doesnot

specifyanypadding(incontrastto

IEEE802.3),Ethernetexpectsatleast

46bytesofdata.

oData(IEEE802.3)--Datacontainedin

theframe.Afterphysicallayerandlink

layerprocessingiscomplete,thisdata

issenttoanupper-layerprotocol.The

upper-layerprotocolmustbedefined

withinthedataportionoftheframe,if

atall.

48

EthernetandIEEE802.3FrameFields

(Conf)

oIfdataintheframeisinsufficienttofill

theframetoitsminimuin64-byte

size,paddingbytesareinsertedto

ensureatleasta64-byteframe.

oFrameCheckSequence(FCS)—

Containsa4-bytecyclicredundancy

check(CRC)value.TheCRCiscreated

bythesendingdeviceandrecalculated

bythereceivingdevicetocheckfor

damagedframes.CRC定义

49

虚网标记

VLANTagging

oEthernetframeformatextensionstosupport

VirtualLocalAreaNetwork(VLAN)Tagging

oTheVLANprotocol(802.lq)permitsinsertionof

anidentifier,or“tag”，intotheEthernetframe

format

oVLANTaggingprovidesvariousbenefits

Easingnetworkadministration

Allowingformationofworkgroups

Enhancingnetworksecurity

oThe4-byteVLANtagisinsertedbetweenthe

“Source”MACAddressfieldand“Length/Type”

field

50

Formatof:

802.3/802.1Q

802.3DestSourceTypeDataFCS

「Maxi518]Addr(6)Addr(6)(2)(Max1496；(4)

802.1QDestSourceVLANVLANTypeDataFCS

[Maxl518]Addr(6)Addr(6)Type(2)ID⑵(2)(Max1496：(4)|

51

混合模式

Promiscuousmode

oPromiscuousmodeisaconditionwherethe

networkinterfacecontrollerwillpassallframes,

regardlessofdestinationaddress,uptothehigher

levelnetworklayers.Normallythenetwork

controllerwillonlypassupframesthathave

thatdevice'sdestinationaddress.However,when

putinpromiscuousmode,allframesarepassedon

upthenetworkstackregardlessofdestination

address.Promiscuousmodeisusuallyusedby

networkmonitoringtoolsandtransparentbridges

(and,frequently,bynetworkcrackerstryingto

snatchpasswords,orotherdatathey'renormally

notabletosee,offthewire).

52

Reference

o/ethernet/

descript-10quickref.html

o/ethernet/

100mbps.html

o/ethernet/

o/univercd/cc/td/

doc/cisintwk/ito_doc/ethernet.htm

o/consortiums/fe/

o/research/

ge.html

53

100MbpsEthernet

ApplicationSoftware

andUpper-layerProtocols

TCP/IP

Carddriver

802.3MediaAccessControl

Sublayer

100Base-T

PhysicalLayerlOOBaseTXlOOBaseFX100BaseT4

54

10M和100M以太网区别

Differencesin10/1OOMEthernet

oSpeed

100Mbps

oCoding

•MLT3

oAuto-Negotiation

anoptionalpartoftheEthernetstandardthat

makesitpossiblefordevicestoexchange

informationabouttheirabilitiesoveralink

segment.

allowsthedevicestoperformautomatic

configurationtoachievethebestpossible

modeofoperationoveralink.

oCableSpecification

55

FLPS百兆以太网快速链路脉冲

FLPs-WOBaseTastLinkulses

olOOBaseTusespulses,calledfastlink

pulses(FLPs),tocheckthelinkintegrity

betweenthehubandthelOOBaseT

device.

oFLPsarebackwardcompatiblewith

lOBaseTnormallinkpulses(NLPs).But

FLPscontainmoreinformationthanNLPs,

andareusedintheauto-negotiation

processbetweenahubandadeviceona

lOOBaseTnetwork.

56

主要设备

MajorDevices

oNetworkInterface

Card

oTransceiver

oRepeater

oBridge____

oSwitch

__1

r)7

千兆以太网概述

GigabitEthernetOverview

oGigabitEthernetisanextensionoftheIEEE802.3

Ethernetstandard-802.3z.GigabitEthernetoffers

1000Mbpsofrawdatabandwidthwhilemaintaining

compatibilitywithEthernetandFastEthernetnetwork

devices.

Newfull-duplexoperatingmodesforswitch-to-switch

andswitch-to-end-stationconnections

Half-duplexoperatingmodesforsharedconnections

usingrepeatersandCSMA/CD

Usesthesameframeformat,framesize,and

managementobjectsusedinexistingIEEE802.3

networks

Initiallyoperateoverfiberopticcabling,butwillbe

implementedoverCategory5unshieldedtwisted-pair

(UTP)as802.3ab.

58

GigabitEthernet

'w|CaptureI<Unkno

59

到千兆以太网的过渡

MigrationtoGigabitEthernet

oUpgradeswitch-to-switch

links--1000Mbps

oUpgradeswitch-to-server

links--1000Mbps

oUpgradeaFastEthernetbackbone

oAllowsserverstobeconnecteddirectly

tothebackbonewithGigabitEthernet

NICs

oUpgradehighperformancedesktops

60

IEEE802.3Ethernet

IEEE802.3

LLCProtocolStackofGE

IEEE802.3

CSMA/CD

aIEEE802.2LLC

IEEE802.3

PhysicalLayer

CSMA/CDFullDuplex

MediaAccessControl(MAC)

ANSIX3T11FibreChannel

8B/10B

FC-4UpperLayerEncode/Decode

Mapping

FC-3CommonSerializer/Deserializer

Services

FC-2SignalingConnector

FC-1

Encode/DecodeIEEE802.3zGigabitEthernet

FC-0Interface

andMedia61

8B/10BEncoder

汽TM⑷DataByte

LESOFEIGHT书ITCODEGROUPS

ActualByteRD・RD+Effecton

BeingEncodingEncocfingRDafter

EncodedValueValue